Rockets and missiles are often guided by hot gas thruster valves that expel hot gas generated by the combusting of a solid propellant. Because of the difficulty associated with controlling and containing the hot gas, these valves are generally configured as on/off valves or pulse width modulated valves. A disadvantage to these types of valves is that their abrupt movement, on and off, can cause undesirable vibration and jitter in the vehicle and/or in the vehicle's guidance system. Another disadvantage is that these valves either provide maximum thrust or zero thrust and do not have the capability of providing a thrust level in between. In addition, the pressure of the hot gas is dependent upon the exhaust area of these valves, and is thus subject to the ripple creating an uncertainty in pressure level. A system of proportional valves can provide trimming of the exhaust area, which in turn allows pressure control of the solid propellant motor. This feature can be exploited to also provide mission extension by selectively effecting high and low pressure, or high and low flow segments of the overall mission. This leads to longer range and higher efficiency of the rocket or missile. On/off valves lack this capacity.
Accordingly, a need exists for a hot gas thruster valve that can operate smoothly and also provide intermediate thrust levels and solid propellant gas generator pressure control.